© Author(s) 2021. CC Atribution 4.0 License Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina Poznokarbonska biota z območja rudnika železa Ljubija v Bosni in Hercegovini Aleksej MILOŠEVIĆ 1 , Alexander S. ALEKSEEV 2,3 , Elena ZAYTSEVA 2 , Matevž NOVAK 4 , Tea KOLAR-JURKOVŠEK 4 & Bogdan JURKOVŠEK 5 1 University of Banja Luka, Faculty of Mining, e-mail: aleksej.milosevic@rf.unibl.org; 2 Faculty of Geology, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia; e-mail: aaleks@geol.msu.ru; ezaitseva@mail.ru; 3 Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya 123, 117647 Moscow, Russia; 4 Geological Survey of Slovenia, Dimičeva ulica 14, SI-1000 Ljubljana, Slovenia; e-mail: matevz.novak@geo-zs.si; tea.kolar-jurkovsek@geo-zs.si 5 Kamnica 27, 1262 Dol pri Ljubljani, Slovenia; e-mail: geolog.bj@gmail.com Prejeto / Received 14. 4. 2021; Sprejeto / Accepted 1. 7. 2021; Objavljeno na spletu / Published online 19. 7. 2021 Key words: Upper Carboniferous, Pennsylvanian, Algae, Foraminifera, Conodonts, Olistoliths, Sana-Una Paleozoic Ključne besede: zgornji karbon, pennsylvanij, alge, foraminifere, konodonti, olistoliti, Sansko-unski paleozoik Abstract The Olistostrome member of the Sana-Una Paleozoic complex of the Ljubija ore mine in Bosnia and Herzegovina contains limestone fragments of pebble to block size that have been examined paleontologically. The recovered conodont fauna of the first sample is characterized by the species Declinognathodus lateralis, Idiognathoides sulcatus sulcatus and Idiognathodus sp. confirming its mid-Bashkirian age. This report is the first on the occurrence of these taxa in the area. The second sample with chaetetid demosponges yields an abundant diversified microbiota consisting of cyanobacteria, algae and foraminifera. Chlorophyts are marked by the common siphonoclad occurrence of Donezella lutugini and D. lunaensis, whereas rhodophyts include rare representatives of Stacheia, Stacheoides, Pseudoungdarella and Masloviporidium. The presence of Asphaltinella horowitzi and Aphralysia carbonaria of unclear taxonomic position is also documented. Pseudostaffellids, eostaffellids and other foraminifera, mostly endothyrids are present. The examined associations of fossils point to the Bashkirian age of the primary rock that originated in a very shallow habitat most probably linked to a high-energy reef environment. Izvleček Olistostromski člen v Sansko-unskem paleozojskem kompleksu rudnika Ljubija v Bosni in Hercegovini vsebuje apnenčaste prodnike in bloke, ki so bili paleontološko raziskani. Konodontno favno prvega vzorca označujejo Declinognathodus lateralis, Idiognathoides sulcatus sulcatus in Idiognathodus sp., ki dokazujejo njegovo srednjebaškirijsko starost. To je prvo poročilo o pojavu teh taksonov na tem območju. Drugi vzorec s hetetidno demospongijo vsebuje bogato in raznoliko mikrobioto, ki jo sestavljajo cianobakterije, alge in foraminifere. Med klorofiti so pogoste sifonoklade Donezella lutugini in D. lunaensis, med rodofiti pa so redki predstavniki Stacheia, Stacheoides, Pseudoungdarella in Masloviporidium. Dokumentirana je tudi prisotnost Asphaltinella horowitzi in Aphralysia carbonaria z nejasnim taksonomskim položajem. Foraminifere zastopajo psevdostafelide, eostafelide in manjše foraminifere, večinoma endotiride. Raziskana združba kaže na baškirijsko starost izvorne kamnine, ki je nastala v zelo plitkem habitatu, verjetno povezanim z visokoenergijskim grebenskim okoljem. GEOLOGIJA 64/1 , 65-80, Ljubljana 2021 https://doi.org/10.5474/geologija.2021.004 Introduction The Ljubija siderite ore field is located around 200 km northwest of Sarajevo (Fig. 1), in Bosnia and Herzegovina, and belongs to the Sana-Una Paleozoic complex (Hrvatović, 2006). Togeth- er with the Mid-Bosnian Schist Mountains, the Paleozoic strata of eastern and southeastern Bos- nia represents the Paleozoic complexes of the Di- narides in Bosnia and Herzegovina that are not genetically related to the Mesozoic-Paleogene evolution of the Tethys (Hrvatović, 2006). The boundaries of the Sana-Una Paleozoic complex are defined based on an unclear contact with younger strata (northeastern and southwest- 66 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK ern boundary), and in parts where tectonic ele- ments are not expressed, the boundaries are set based on topographic criteria (Jurić, 1971). In the northwest, the Sana Paleozoic complex is sepa- rated from the Banija by the Una River, and in other parts it is limited by the Mesozoic strata; to the south is the front of the Sana Nappe, to the east the border of the Jurassic and Cretaceous formations, and to the north the inner ophiolite zone of Kozara. The area features interesting ge- ological phenomenon due to the well known and potentially exploited deposits of iron and other raw minerals. The first studies of the Sana Paleozoic complex commenced with the investigation of Austrian geologists (e. g. Mojsisovics et al., 1880) and later the iron ores near Ljubija were part of detailed examinations of Katzer (1910, 1921, 1926). The new evidences were obtained interpreting the Carboniferous sediments as turbidite deposits that contained mineralized limestone olistoliths. The entire Carboniferous sequence has been se- verely hydrothermaly influenced (Stefanovska, 1990). Later, these Carboniferous sediments were genetically considered as typical flysch deposits where a significant amount of limestone olisto- liths occur (Grubić et al., 2000). Katzer (1926) was the first who considered the Paleozoic formations of the wider area of Ljubija to be Late Carboniferous in age and his view has been accepted by later researchers (Simić, 1940; Heritsch, 1940; Crnolatac, 1949; Noeth, 1952). However, paleontologic evidence for the Early Carboniferous age of the limestone in the Sa- na-Una Paleozoic complex was provided by Ko- stić-Podgorska (1955) based on the coral fauna. Data on fossils found in the Sana-Una Paleozoic complex were successfully systematized by Jurić (1971). The faunas obtained in the olistoliths ev- idenced the Devonian, Early and Late Carboni- ferous and according to Grubić et al. (2000) the age of the Olistostrome member is assigned to the topmost Early to Late Carboniferous. An important study on siderite-barite-pol- ysulfide deposits of the Middle Dinarides, con- sidering the Ljubija ore region, was published by Palinkaš (1990). In the last decades the research concept has been severely based on the metallo- geny of this ore region. More recent geochemi- cal examinations of the Ljubija mines resulted in interpretation that ore origin is hydrother- mal-metasomatic and that the mineralization is of Permian age (Strmić-Palinkaš et al., 2009; Garašić & Jurković, 2012; Palinkaš et al., 2016). More recent data on the geology and metalloge- ny of the Ljubija ore region are presented in the works of Grubić et al. (2015) and Milošević et al. (2017). Conodonts have demonstrated their value for biostratigraphy and they are one of the leading microfossil groups in the interpretation of the biostratigraphy of Paleozoic and Triassic ma- rine strata. As they have proven their practical value as parastratigraphic fossils, the main goal of our study is to examine conodont faunas from the Ljubija area. The conodonts of the Sana-Una Paleozoic strata are scarce. During the mapping of the Geological map of SFRY 1: 100,000 they were identified and described at two locations sites (Jurić, 1975). The tentaculite finds at Blagaj already determined in the field the pre-Carbon- iferous age of the limestones, and based on litho- logical analogy with the Devonian limestones of Družetić in western Serbia, a Devonian age was assumed, which was confirmed by the cono- dont examination (Spasov & Filipović, 1966). The conodont fauna from the Blagaj limestone is characterized by the presence of representa- tives of the genus Palmatolepis, which first ap- pears in the Late Devonian. The list of the iden- tified taxa includes: Palmatolepis glabra glabra, P. minuta, P. subperlobata, Polygnathus glabra glabra, Po. nodosocostata nodosocostata that are ranged in the interval of the Famennian crepida- rhomboidea zones (Spasov & Filipović, 1966). Another locality is a site south of Prijedor. A conodont fauna of a smaller limestone block, was discovered in a road-cut Ljubija - Sanski Most, about 2 km south of th Adamuša opencast mine. Dark grey limestone contains a rich brachiopod and cephalopod fauna (Stojanović-Kuzenko, 1967); the conodont fauna recovered from this block yields Gnathodus bilineatus and Lochriea commutata commutata ( S p a s o v & F i l i p o v i ć , 1966). This site was recollected by Ramovš (1990) who added to these listed conodont taxa also L. mononodosa and L. nodosa that enabled this fauna to be re-assigned to the nodosa Zone (Vi- sean, Early Carboniferous). The purpose of this study is to examine cono- dont fauna of newly collected samples from the Ljubija mine area, as well as to provide additional data from another sample with a demosponge specimen obtained in a carbonate olistolith from the Adamuša site. The latter sample yields rich algal and foraminiferal associations that are also documented herein. The biostratigraphic and paleogeographic significance of the determined taxa is also provided. 67 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina Materials and methods For micropaleontologic study the conodont sample AT-1 (Fig. 1) was collected (by BJ and TKJ) in the Adamuša opencast mine in 2019 dur- ing the field trip of the Congress of geologists in Bosnia and Herzegovina. The collecting of this bed was repeated as this sample proved to be productive for conodonts, and thus an additional quantity of the rock was provided in 2020 (by AM). The coordinates of the sample AT-1 are: 44° 54’ 34’’ E; 16° 36’ 18’’ N. For this study we added information about the sample with a demospon- gia specimen that was collected in 1974 near the location of the conodont sample AT-1, a locality that is today already flooded; the specimen is housed in the Paleontological collection of Jur- kovšek, Dol pri Ljubljani under the inventory number BJ 49. Another sample (BL-1) for cono- donts was collected in the locality Blatnjak (co- ordinates 44° 50’ 43’’ E; 16° 48’ 04’’ N) that turned out to be devoid of microfauna. The sample AT-1 with a total rock weight of 6 kg was processed for conodonts. A standard tech- nique for processing conodont samples with the use of diluted acetic acid (5-8 %) was applied and followed by heavy liquid separation. The labo- ratory preparation was carried out at the Geo- logical Survey of Slovenia, Ljubljana where the residue is also stored in the micropaleontological collection and inventoried under the repository number GeoZS 6219 and 6220. The illustrated conodont elements presented in this paper were photographed by the JEOL JSM 6490LV Scan- ning Electron Microscope at the Geological Sur- vey of Slovenia. A total of 11 petrographic thin sections have been made from the host rock from the sample with demospongia (sample BJ). Three thin sec- tions were stained by Alizaren Red S and K-fer- ricyanide. All thin sections were photographed with magnifications ×12.5, ×25 and ×50. All 11 thin sections were used also for the study of the foraminifera and algae. Foraminifera occur in all of the studied thin sections. Geological setting The Sana-Una Paleozoic complex is located east of the Una River. It extends over the area from Novi Grad through Prijedor to Sanski Most, Budimlić Japra, Ključ and Mrkonjić Grad where the most widespread strata belong to the Javorik flysch formation (Fig. 2). The Ljubija deposits are set in its Carbonifer- ous part belonging to the Javorik flysch formation where the majority of the mineral resources are emplaced within the Olistostrome member. The Javorik flysch formation is well exposed in the Adamuša and Tomašica opencast mines that is, accoring to Grubić et al. (2015), composed of three members, i.e., the Pre-flysch and Lower flysch, Olistostrome member and Upper flysch (Fig. 2). The basal unit of the Javorik flysch forma- tion is the Pre-flysch and Lower flysch member consisting of dark argillaceous schists with al- ternation of medium-grain sandstone. It is well studied in the Adamuša opencast mine, in a core of large anticline structure. This member was probably formed in a deeper marine environment (Grubić et al., 2015). S a n a V r b a s S a n a U n a U n a S a v a Banja Luka Bihać Sanski Most Prijedor 0 25 km 50 km BOSNIA AND HERZEGOVINA CROATIA AT-1 BL-1 Novi Grad Fig. 1. Index maps with the location of the Ljubija ore mine. (a) Map of NW Bosnia and Herzegovina with mar- ked areas of the Sana-Una Paleozoic complex (gray). Red dots indicate the po- sition of the examined samples. (b) Geographic position of the area shown in Figure 1a; area of Bosnia and Herzegovina marked in green. 68 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK Pre-flysch and Lower flysch: siltstones, sandstones, shales and phyllitoids Olistostrome member: flysch matrix (siltstones, sandstones, shales), olistolithic blocks (limestone, dolostone), mineralized bodies (siderite, ankerite) and autoclastic melange Upper flysch: siltstones, metasiltstones, sandstones and shales Bobovac breccias White sandstones Polygenic conglomerates Red and white sandstones Red siltstones and sandsones Limestones, marly limestones, marlstones and breccias (Werfen formation) Limestones, dolostones with chert and silicious marls Dolostones with limestones and marl intercalations Marls, shales, limestones and sandstones and locally re-deposited Fe ore Neogene- Quaternary Upper Triassic Middle Triassic Lower Triassic Upper Carboniferous Lower and Middle Carboniferous Permian - Triassic 0 50 m Keratophyres and rhyolites Spillites and tuffs AT-1 BL-1 Fig. 2. Schematic lithostratigraphic column of the Sana-Una Paleozoic complex (modified after Grubić et al., 2015). 69 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina The Pre-fysch and Lower flysch member is overlain with the deposits of Olistostrome mem- ber. The thickness of this member varies between 100 to 300 m. It consists of flysch matrix with embedded carbonate olistoliths - boulders and blocks and their mineralized parts. The minerali- zed bodies are represented by siderite and anker- ite. Carbonate fragments and blocks or boulders of the Olistostrome member include black mic- rite, dark grey organogenic sparite (rich in fos- sils), dolomitic limestone and dolostone, ankeritic limestone and ankerite. Within the Olistostrome member some authors distinguished more units, i.e. a Siderite-limonite member, and Wild flysch and Middle flysch (Grubić & Protić, 2003; Garašić & Jurković, 2012). The Olistostrome member was formed under deep-water conditions (Grubić & Protić, 2003) found in the core of the Sana an- tiform. The studied samples originate from this unit. The youngest member of the Javorik flysch for - mation is the Upper Flysch member that is also the most widespread member of the Sana-Una Paleozoic complex. It is well exposed in the Tomašica opencast where it attains thickness of 70 m. It is mainly formed of sandstone-siltstone flysch. Due to Mn oxides and hydroxides particu - larly, its lower part is black in colour (Grubić & Protić, 2003). The Permian-Triassic clastic formation ap- pears in discontinuously exposed zones in the north and south limb of the Sana antiform and south from the Sana Nappe. Its maximum thick- ness is estimated to 150 m. According to Grubić and Protić (2003), five members can be distin- guished: a) Bobovica breccia, b) white sandstone, c) white and red sandstone, d) polygenous con- glomerate and e) red sandstone and siltstone. Also present are porous dolomite (of a rau- hwacke-type), and siderite veins, up to 40 cm long in some places. The colourful Werfen strata are overlain by limestone and dolomite, covered by a Ladinian volcanogenic-sedimentary porphyrite-chert for- mation. Among the younger sedimentary rocks, only lacustrine Neogene - Quaternary deposits are present. The tectonic history of this area is very com- plex as it was a consequence of Hercynian, Cim- merian and Alpine deformation phases. Hercyni- an events left their signatures only in the Javorik flysch for mation, i n the for m of fold s whose B -a xes have an azimuth of 10 to 40°. The dispersion of the B-axis is a consequence of Alpine refolding (Grubić & Protić, 2003). Results Microfacies The microfabric of the rock sample BL-1 with chaetetid demosponge is irregular, peloidal bi- oclastic grainstone to packstone. In one of the thin-sections also biosparite micro-breccia (rud- stone) is present. Bioclasts and peloids (algal and microbial) predominate. Intraclasts and pellets also occur. Bioclasts are represented by algae, cyanobacteria and foraminifera are most common. Many echi- noderm (mostly crinoid) fragments also occur together with rare thin bivalve shells, small gas- tropods and ostracods. Very rare are fragments of brachiopods. Intraclasts contain bioclasts and pelmicrite. Echinoderm fragments are up to 1 cm, most of them, and also other bioclasts, exhibit abraded margins with replacements by micrite. The rock is crosscut with several thin white calcite veins and a few thicker ones. It exhibits weak to strong irregular stylolitization. Foraminifera Foraminifera in the BJ 49 sample belong to groups of pseudostaffellids, eostaffellids and smaller foraminifera, mostly endothyrids. De- termination on a species level is hindered be- cause of the lack of oriented sections. In the studied material, several specimens of the genus Pseudostaffella are found, which in general can be assigned to the Pseudostaffella ex gr. antiqua (Dutkevitch) species group (Rauser-Chernouso- va et al., 1951). By the position of the coiling axes and the character of the chomata, the specimens are identified as Pseudostaffella antiqua (Dut- kevitch), Ps. grandis Schlykova, Ps. cf. posteri- or Safonova, and ?Ps. cf. proozawai Kireeva (Pl. 1, Figs. a-e). In general, these forms are slightly smaller in size compared to those common in the Russian Platform and in the Urals (Grozdilova & L ebe deva, 1950; R au se r- C he r nou sova et a l., 1951). Among forms assigned to the genus Eostaf- fella, the following species are identified: Eo- staffella pseudostruvei chomatifera Kireeva, E. parastruvei chusovensis Kireeva, and E. cf. parastruvei chusovensis Kireeva (Pl. 1, Figs. f-i). The genus Plectostaffella is represented by Plectostaffella varvariensis (Brazhnikova & Potievskaya), P. ex gr. bogdanovkensis Re- itlinger; P. cf. irregularia (Reitlinger); P. o vo i d e a - formis (Reitlinger) (Pl. 1, Figs. j-n). Also present is the genus Semistaffella with the species S. variabilis (Reitlinger), S. primitiva (Reitlinger), 70 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK Plate 1. Fusulinoidean and smaller foraminifera from Ljubija, sample BJ 49. Scale bar is 200 microns. (a): Pseudostaffella antiqua (Dutkevitch), (b, c): Pseudostaffella grandis Schlykova, (d): Pseudostaffella cf. posterior Safonova, (e): ?Pseudostaffella cf. proozawai Kireeva, (f): Eostaffella pseudostruvei chomatifera Kireeva, (g): Eostaffella parastruvei chusovensis Kireeva, (h): Eostaffella cf. parastruvei chusovensis Kireeva, (i): Eostaffella sp., (j): Plectostaffella varvari- ensis (Brazhnikova & Potievskaya), (k): Plectostaffella ex gr. bogdanovkensis Reitlinger (l): Plectostaffella ovoideaformis (Reitlinger), (m): Plectostaffella cf. irregularia (Reitlinger), (n): Plectostaffella sp., (o): Semistaffella variabilis (Reitlinger), (p): Semistaffella primitiva (Reitlinger), (q): Semistaffella minor (Rauser-Chernousova), (r): Parastaffella cf. struvei (Möller), (s): Parastaffella cf. poststruvei Rauser-Chernousova, (t): Parastaffella sp., (u): ?Endothyra sp., (v): Endothyra bradyi sim- plex Reitlinger, (w, x): Endothyra sp. (E. ex gr. bradyi Mikhailov), (y): Endothyra mutabilis Reitlinger, (z): Endothyra cf. mosquensis Reitlinger, (za): Endothyra bradyi compressa Reitlinger, (zb): Endothyra sp. (E. cf. mosquensis Reitlinger), (zc): Planoendothyra ex gr. spirilliniformis (Brazhnikova & Potievskaya), (zd): Biseriella minima (Reitlinger), (ze): Biseriella ex gr. moderata (Reitlinger). 71 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina and S. minor (Rauser-Chernousova) (Pl. 1, Figs. o-q). A few lenticular forms with acute margins belong to Parastaffella cf. struvei (Möller) and P. cf. poststruvei Rauser-Chernousova (Pl. 1, Figs. r-t). Endothyrids are represented in significant amounts. The species Endothyra ex gr. brad- yi Mikhailov, E. bradyi compressa Reitlinger, E. mutabilis Reitlinger, E. cf. mosquensis Re- itlinger, and Planoendothyra ex gr. spirillini- formis (Brazhnikova & Potievskaya) were recog- nized (Pl. 1, Figs. u-zc). Accompanied foraminifera, occuring in small amounts are Globivalvulinidae (Biseriella minima (Reitlinger) and B. ex gr. moderata (Re- itlinger) (Pl. 1, Figs. zd, ze), Bradyinidae (Brady- ina ex gr. nautiliformis Möller and ?B. pseudo- nautiliformis Reitlinger) (Pl. 2, Figs. a-c), Palae- otextularioidea (Koskinobigenerina aljutovica (Reitlinger); Koskinotextularia posteximium (Reitlinger), Deckerellina cf. mirabilis Reitlinger (Pl. 2, Figs. d-g) and Neoarchaediscus postrugosus (Reitlinger) (Pl. 2, Fig. h), Tuberitina bulbacea Galloway & Harlton (Pl. 2, Fig. i), ?Tolypammina ex gr. complicata Reitlinger (Pl. 2, Fig. j), Post- monotaxinoides cf. horridus (Lipina) (Pl. 2, Fig. k), and Pseudoglomospira cf. elegans (Lipi- na) (Pl. 2, Fig. l). In the International Stratigraphic Scale (Aretz et al., 2020), the base of the Bashkirian Stage (base of the Pennsylvanian) is marked by the appearance of the conodont Declinognathodus noduliferus. This level correlates with the base of the ammonoid Homoceras Zone and the base of foraminiferal Plectostaffella bogdanovkensis Zone. The P. bogdanovkensis Zone is traced in the Urals (Kulagina, 2014), in the Caspian Region (Zaytseva & Klenina, 2008), and in Middle Tien- Shan (Dzhenchuraeva et al., 2013). The appearance of the species Pseudostaffella antiqua (Dutkevitch) is a noticeable level in the evolution of fusulinids corresponding to the middle part of the lower Bashkirian (the base of the Akavasian Regional Substage in Urals or Severokeltmenian Regional Substage of the Rus- sian Platform) and is distinguished as the rap- id diversification of pseudostaffellids (Kulagina & Gorozhanina, 2019). The represented species of the genera Eostaffella, Plectostaffella and Semistaffella are characteristic of the lower Bash- kirian. The species Plectostaffella varvariensis (Brazhnikova & Potievskaya) is known from the top of the Serpukhovian. P. bogdanovkensis is a zonal marker of the Serpukhovian/Bashkirian boundary of the East European Platform and the Urals. The genus Semistaffella appears slight- ly higher. There are transitional forms between them as well as between Semistaffella and pri- mitive Pseudostaffella. During the Early Carboniferous, the gen- era and species of the Ozawainellidae and Staffellidae were common in shallow carbonate shelves and in basins of nearly all regions of the world (BouDagher-Fadel, 2008). The diversity of the fusulinids and their related forms increased at the Serpukhovian-Bashkirian boundary. Fo- raminiferal provinces have been clearly distin- guished already since late Famennian (Lipina, 1973) with three different provinces becoming recognizable: the East European Basin that are characterized by an abundance of Eostaffella and Bradyina; the Tethyan Realm, where the palaeotextulariids were abundant; and the North American Realm, where Bradyina did not appear before the Bashkirian. During the Late Carboniferous (Bashkirian to Gzhelian), the endothyrids, staffellids and brady- inids may have colonized their habitats within or in adjoining high-energy environments (Din- gle et al., 1993; Della Porta et al., 2005). The en- dothyrids were common in low- and high-energy settings. Their exclusion from lagoonal environ- ments with a restricted circulation and varia- ble salinity suggests that these forms preferred open-marine environments (Della Porta et al., 2005). The lenticular staffellids are abundant in higher energy, reef facies, whereas the subspheri- cal forms were common in the quieter, back reef facies (Dingle et al., 1993), in the shallowest set- ting and in paleoenvironments characterized by abnormally high temperatures and salinity. The Bradyinidae were probably epiphytes and Brady- ina is interpreted as a shallow-water taxon adapted to life in current-swept environments (Gallagher, 1998; Gallagher & Somerville, 2003; BouDagher-Fadel, 2008). Cyanobacteria and algae The remains of cyanobacteria are very com- mon in the studied thin sections (Pl. 2, Figs. m-o). They are similar to the remains of filament-form - ing and coccoid bacteria described by Mamet & Preat (2010) from Bashkirian foraminifer zones 20 and 21 of Arctic Alaska. Besides the remains of Girvanella sp. (Pl. 3, Fig. d) also Stipulella fascicularis Maslov (Pl. 2, Figs. r-s) is identified. This species was described from the Lower Car- boniferous of the Moscow Basin (Maslov, 1956). It is distributed in the Kizelian Regional Substage of the upper Tournaisian and the upper part of 72 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK Plate 2. Smaller foraminifera and cyanobacteria from Ljubija, sample BJ 49. Scale bar is 200 microns. (a-c): Bradyina ex gr. nautiliformis Möller (?B. pseudonautiliformis Reitlinger), (d): Koskinobigenerina aljutovica (Reitlinger), (e): Koskinobigeneriidae, (f): Koskinotextularia posteximium (Reitlinger), (g): Deckerellina cf. mirabilis Reitlinger, (h): Neoarchaediscus postrugosus (Reitlinger), (i): Tuberitina bulbacea Galloway & Harlton, (j): ?Tolypammina ex gr. compli- cata Reitlinger, (k): Postmonotaxinoides cf. horridus (Lipina), (l): Pseudoglomospira cf. elegans (Lipina), (m): a – Filament- forming and cocoid cyanobacteria, b – Donezella sp., c – Anthracoporellopsis sp., (n, o): Filament-forming and cocoid cyanoba- cteria, (p): Oncolites with Tolypammina fortis Reitlinger, (r): a – Stipulella fascicularis Maslov, b – Donezella sp., (s) Stipulella fascicularis Maslov. 73 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina Plate 3. Green and red algae and problematica from Ljubija, sample BJ 49. Scale bar is 200 microns. (a, b, c): Donezella lutugini Maslov, (d): a – Donezella lutugini Maslov, b – Girvanella sp., (e, f): Donezella lunaensis Racz, (g): Dvinella cf. bifurcata Maslov & Kulik, (h): Proninella enigmatica Mamet & Roux, (i): Anthracoporellopsis cf. machaevii Maslov, (j): a – Pseudoungdarella sp. (?P. cf. linearis R. Ivanova), b – Praedonezella cf. cespeformis Kulik, c – ?Donezella sp., (k): a - Stacheia cf. marginulinoides Brady, b – Stacheoides cf. meandriformis Mamet & Rundloff, (l): Masloviporidium de- licata (Berchenko), (m): Stachaeoides sp., (n): Asphaltinella horowitzi Mamet & Roux, (o): Aphralysia carbonaria Garwood. the Serpukhovian Stage of the Urals (Ivanova, 2013), in the Zapaltyubian Regional Substage of the Serpukhovian Stage of the Donets Basin (Berchenko, 1983), and the Visean and Namurian of the Paleo-Tethys (Mamet & Roux, 1983). Forms similar in morphology, described as Ortonellop- sis laxa Vachard & Cozar were found in the up- per Visean - lower Serpukhovian of Montagne Noire, France (Vachard et al., 2016). Rare algae also occur in thin sections, how- ever of poor preservation. Chlorophyta, repre- sented mainly by Siphonocladales, and also in- cluding representatives of the genera Donezella, Dvinella, Proninella, Exvotarisella, Anthra- coporellopsis are distinguished by a relative diversity. Donezella is more common with two species: Donezella lutugini Maslov (Pl. 3, Figs. a-d) and D. lunaensis Racz (Pl. 3, Figs. e-f). Both species are characteristic of the Bashkirian and are distributed up to the Asselian Stage of the Lower Permian in Arctic Canada (Mamet et al., 1987), northern Spain (Mamet & Villa, 2004), northwestern Serbia (Pajić & Fillipović, 1995) and in Urals, Donets Basin and Tajikistan (Iva- nova, 2013). Fragments of Dvinella cf. bifur- cata Maslov & Kulik (Pl. 3, Fig. g), Proninella enigmatica Mamet & Roux (Pl. 3, Fig. h) and Anthracoporellopsis cf. machaevii Maslov (Pl. 3, Fig. i) thalli were identified. The species Dvinella bifurcata is known from the Middle Carboniferous of the Urals and the East Euro- pean Platform, from the Bashkirian of north- western Serbia (Pajić & Fillipović, 1995), and in northern Greenland it occurs in the Moscovian Stage (Mamet & Stemmerik, 2000). Proninella enigmatica is described from the upper Visean of North America (Mamet & Roux, 1978). In the Urals, it was reported from the Tournaisian, upper Visean and Bashkirian (Ivanova, 2013). Anthracoporellopsis machaevii is described from the Middle Carboniferous of the Donets Basin (Maslov, 1956). In Western Europe, it is found in Visean deposits. The stratigraphic range of this species in the Urals is from the upper Visean to the Lower Permian (Ivanova, 2013). In the Moscow Basin it is found in the up- per Visean (Gibshman & Alekseev, 2017). The studied material also contains two spe- cies of Chlorophyta of unclear taxonomic posi- tion: Asphaltinella horowitzi Mamet & Roux and Aphralysia carbonaria Garwood (Pl. 3, Figs. n-o). The first species is described from the Vi- sean of Canada, southwestern Alberta (Petryk & Mamet, 1972) and is especially abundant in the Serpukhovian. It occurs in the upper Visean of the Moscow Basin (Gibshman & Alekseev, 2017), and in the Bashkirian of the Urals (Ivanova, 2013). The species Aphralysia carbonaria is wide- spread in the Dinantian of England and is known from the upper Serpukhovian of the Donets Ba- sin (Berchenko, 1983). Rhodophyta include sporadic isolated repre- sentatives of the genera Stacheia, Stacheoides, Pseudoungdarella, and Masloviporidium (Pl. 3, Figs. j-l) The species Stacheia marginulinoides Brady is distributed in the upper Visean and Serpukhovian of the Paleo-Tethys (Mamet & Roux, 1983) and from the Serpukhovian-Bash- kirian boundary strata of Alaska (Mamet & Preat, 2010). On the western slope of the South Urals, it was found in the Bashkirian strata. Stacheoides meandriformis Mamet & Rundloff is a cosmopolitan species and is known from the Visean of France, Belgium, Morocco, USA, from the Upper Carboniferous of the Canadian Arctic Archipelago, the Permian of Turkey, and the Serpukhovian Stage ranging from the Lower to Upper Carboniferous of the Urals (Ivanova, 2013). The species Masloviporidium delicata (Berchenko) is described from the Serpukhovi- an Stage of the Donets Basin (Berchenko, 1982). Its geographic distribution is in North Africa (Algeria) and North America where it was as- signed to the uppermost Serpukhovian and Bashkirian stages (foraminiferal zones 20 and 21) (Groves & Mamet, 1985). In the Urals, it is known from the upper Visean to the Bashkirian Stage (Ivanova, 2013). The species Pseudoung- darella linearis Ivanova occurs in the Serpuk- hovian, Bashkirian and Moscovian of the Urals (Ivanova, 2013). Thus, the algoflora in the studied block is rep - resented by forms of wide stratigraphic range and geographic distribution. The most important species among them are Donezella lutugini and D. cf. lunaensis, which were bioherm-formers and rock-formers in the Bashkirian Stage (Iva- nova, 2013; Rodriguez-Castro et al., 2020). Demospongia A specimen of Chaetetes, a hyper-calcified demosponge was collected in the Adamuša open- cast mine (Fig. 3). The demosponge fossil (isomet- ric 5-6 cm large skeleton) occurs in a single clast together with coarse matrix and large crinoidal ossicles. Its surface reveals a skeleton consisting of closely connected tubules (diameter 0.3-0.7 mm) with indicated radial growth direction. Chaetet- ids were previously classified as extinct corals, bryozoans, algae, stromatoporoids and sclero- 74 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK sponges (West, 2011). They grew in very shallow water and formed expansive biostromes (Stan- ton et al., 2016). The fossil record of chaetetids is known worldwide and they are common in strata ranging from the Ordovician through Ju- rassic (West, 2011). The species Chaetetes radians that was first described from the Carboniferous of the Moscow Basin (Fischer, 1837) has been al- ready reported from the Ljubija mine area, i.e., in the Jakarina Kosa locality, near Adamuša where it was collected from Carboniferous strata (Ko- stić-Podgorska, 1959, 1965). Conodonts Despite moderate preservation, five conodont elements can be identified from the sample AT-1 (Fig. 4) at the genus and even species level, which allow dating of the source rock with sufficient accuracy (Fig. 5). The most important specimen is a right P1 element without a free blade, but it has slight- ly curved nodular carina to the rostral margin whose nodes are fused with the nodes of rostral parapet. These characters are indicative for the species Declinognathodus lateralis (Higgins & Bouckaert) described from the Namurian (Al- portian and Kinderscoutian) in Belgium. The species is widely distributed in the lower and middle Bashkirian strata of Great Britain (Hig- gins, 1975), Donets Basin, Ukraine (Nemyrovska, 1999), South Urals, Russia (Kulagina et al., 2014; Nikolaeva et al., 2017), and South China (Hu et al., 2018). In South China, D. lateralis spans in the middle Bashkirian, with its first occurrence (FO) is in the lower part of the Idiognathoides sinuatus Zone, and its lower occurrence (LO) is in the middle part of the “Streptognathodus” expansus M1 Zone (Hu et al., 2019), but in the South Urals it first appears in the lowermost Bashkirian and its FO coincides with the base of the D. noduliferus Zone (Kulagina et al., 2014). Three specimens, which are also uncomplete right P1 elements, possess two narrow nodose parapets separated by relatively deep median trough. They belong to the subspecies Idiogna- thoides sulcatus sulcatus (Higgins & Bouckaert) that was established on left elements only, but Fig. 3. Chaetetes sp. Adamuša, sample BJ 49. Scale bar 10 mm. Fig. 4. Outcrop at the Adamuša iron depo- sit where the limes- tone sample AT-1 was collected. 75 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina 76 A. MILOŠEVIĆ, A. S. ALEKSEEV , E. ZAYTSEVA, M. NOVAK, T. KOLAR-JURKOVŠEK & B. JURKOVŠEK Higgins (1975) illustrated also right elements for this subspecies which are very similar to the ones from Ljubija. This subspecies occurs in the Bashkirian being described from the ammonoid R1-G2 genozones of Belgium (Higgins & Bouck- aert, 1968) and Great Britain (Higgins, 1975), but in South China and the South Urals, Russia, it is found in much younger strata reaching the Bashkirian/Moscovian boundary and even in the lower Moscovian (Kulagina et al., 2001; Hu et al., 2019). The third conodont morphotype is broken P1 element, without ventral part of the free blade and most of dorsal platform. However, the plat- form is very wide with no recognized trough. This element belongs to the genus Idiognathodus without any doubts, but the species identification is not possible, therefore the element is assigned to Idiognathodus sp. only. The FO of the genus Idiognathodus is very im- portant datum plane in the conodont zonations: I. primulus marks the Marsdenian (R2 Genozone) of England (Higgins, 1975) and the mid-Bashkirian Idiognathodus primulus Zone of South China (Hu et al., 2019). However, in the type Bashkirian sections of the South Urals the three Idiognatho- dus species (I. sinuosus Ellison & Graves; I. deli- catus Gunnell and I. primitivus (Nemirovskaya & Alekseev)) occur in the middle Bashkirian in- terval, at the base of the Askynbashian Substage (Kulagina et al., 2001). The joint presence of the species Declinogna- thodus lateralis, Idiognathoides sulcatus sulca- tus and Idiognathodus sp. confirms a mid-Bash- kirian age of the source rocks, which is the Askynbashian and lower Arkhangelskian sub- stages in the Russian stratigraphic nomenclature (Alekseev, 2008). A strange character of the Ljubija conodont assemblage is the absence of Idiognathoides corrugatus (Harris & Hollingsworth) and Id. sinuatus H a r r i s & H o l l i n g s w o r t h , t w o u b i q u i - tous Bashkirian and early Moscovian species, that might be explained by very lower count of the extracted conodont elements (only five). The assemblage belongs to the outer shelf and slope Declinognathodus-Idiognathoides biofacies (Da- vis & Webster, 1985). In the Spanish Pyreneans, the assemblage of the Idiognathodus Zone is similar to the one from Ljubija that is present in the Quinto-Real area in the upper part of the Baserdi Member of the Olazar Formation, in the siliciclastic Kulm-type unit interpreted as Kinderscoutian-Marsdenian in age (Sanz-López & Blanco-Ferrera, 2012). A joint occurrence of several species of Idi- ognathodus and Declinognathodus lateralis is known also in the Namurian C (G1 Zone) lime- stone bands M, N and P in the Lublin Basin, Po- land (Skompski, 1996). In the Donets Basin the FO of Idiognathodus sinuosus is in the Lime- stone F11, upper part of the Mandrykian Region- al Substage, middle Bashkirian, where it occurs together with D. lateralis (Nemyrovska, 1999, 2017). If the Ljubija area has a relation to the North Gondwana Realm, very similar conodont assemblage including D. lateralis and Idiogna- thodus is reported from the Bechar Basin, Alge- ria, from marine inner shelf of the Hassi Kerama Formation of the middle Bashkirian age (Weyant, 1985). Bashkirian conodonts are not common in Great Britain and Western Europe, where they are known only from England (Higgins, 1975), Belgium (Higgins & Bouckaert, 1968), Germany (Meischner, 1970) and Poland (Skompski, 1996). In these countries, conodonts of this age occur only in marine horizons inside of coal-bearing terrestrial sequences, but they are widely dis- tributed in marine carbonate successions of the French and Spanish Pyreneans as well in the Cantabrian Mountains of North Spain. Fig. 5. Conodonts from Ljubija, sample AT-1 (GeoZS 6220). Scale bar is 100 microns. (a, c, d) Idiognathoides sulcatus sulcatus Higgins & Bouckaert, (b) Declinognathodus lateralis (Higgins & Bouckaert), (e) Idiognathodus sp. 77 Late Carboniferous biota from the Ljubija iron mine area, Bosnia and Herzegovina Conclusions Biota obtained from limestone samples of the Olistostrome member of the Adamuša site in the Ljubija area in western Bosnia and Herzegovina have been examined. The limestone sample AT-1 is marked by the joint presence of Declinognatho- dus lateralis, Idiognathoides sulcatus sulcatus and Idiognathodus sp. confirming the mid-Bash- kirian age of the primary rocks. This report is the first of the listed conodont taxa in the area. The Ljubija conodont assemblage is similar to the Declinognathodus-Idiognathoides biofacies of the outer shelf and slope. On the other hand, it can also be compared to an equivalent conodont assemblage of marine inner shelf in Algeria. The chaetetid demospongia (from sample BJ) is associated with a prolific microbiota consisting of cyanobacteria, algae and foraminifera. Micro- facies of the rock is peloidal bioclastic grainstone to packstone. Cyanobacteria are common and exhibit great similarity to the known Bashkirian filament-forming and coccoid bacteria remains. Chlorophyta are dominated by Siphonocladales of relative diversity, among which are common Donezella lutugini and D. cf. lunaensis that are characteristic of the Bashkirian. Rhodophy- ta include sporadic isolated representatives of the genera Stacheia, Stacheoides, Pseudoung- darella and Masloviporidium. The biota also contains two species of unclear taxonomic po- sition, Asphaltinella horowitzi and Aphralysia carbonaria. Foraminiferal assemblage consists of pseudostaffellids, eostaffellids and smaller foraminifera, mostly endothyrids. The presence of the foraminiferal species Pseudostaffella anti- qua points to the Bashkirian age. 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